Some Morphofunctional Features of the Tail of Early Archosaurs in Relation to Swimming Adaptation

Abstract

In ancient and modern aquatic and semi-aquatic tetrapods, several types of structure of the locomotor apparatus are presented, providing various styles of swimming. In the course of evolutionary adaptation to swimming, an important role was played by the morphological transformations of the tail, which often performs the main propulsion function. Modern reptiles (except turtles) swim mainly with the help of horizontal tail bends, while mammals swim either vertical or horizontal ones. Among extinct reptiles, Sauropterygia probably used vertical tail mobility when swimming. In most archosauromorphs, the tail became high, laterally compressed, and they swam mainly with the help of its horizontal movements. Among early archosaurs, Proterohampsians and Doswelliids are distinguished by their wide and dorsoventrally flat tails, which may indicate an adaptation to swimming using its vertical mobility.